<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1 {
            width: 500px;
            height: 500px;
            background-color: #bfa;
            position: relative;
        }
        
        .box2 {
            width: 100px;
            height: 100px;
            background-color: orange;
            position: absolute;
            left: 0;
            right: 0;
            margin: auto;
            top: 0;
            bottom: 0;
        }
    </style>
</head>

<body>
    <div class="box1">
        <div class="box2"></div>
    </div>
</body>

</html>